oauth php

oauth.php

$client = new Google_Client();
$client->setAuthConfig('client_secret.json');
$client->setAccessType("offline");        // offline access
$client->setIncludeGrantedScopes(true);   // incremental auth
$client->addScope(Google_Service_Drive::DRIVE_METADATA_READONLY);
$client->setRedirectUri('http://' . $_SERVER['HTTP_HOST'] . '/oauth/index.php');

$auth_url = $client->createAuthUrl(); ?>

<button onclick="window.location.href = '<?= $auth_url ?>' ">login</button>

<?php
if(isset($_GET['login'])){
    $auth_url = $client->createAuthUrl();

    header('Location: ' . filter_var($auth_url, FILTER_SANITIZE_URL));
}

if(isset($_GET['code'])){
    $client->authenticate($_GET['code']);
    $_SESSION['access_token'] = $client->getAccessToken();
    $client->setAccessToken($_SESSION['access_token']);
    $drive = new Google_Service_Drive($client);
    $files = $drive->files->listFiles(array())->getFiles();;
    echo json_encode($files);
}